This invention relates generally to insulin pumps and, more particularly, to automating insulin pumps to reduce or eliminate the need for patient inputs.
Insulin pumps currently available on the market are open-loop systems that are controlled manually by the user (patient). The user computes the carbohydrate content of a meal or snack to be eaten and enters this information or the corresponding amount of necessary insulin information to the pump manually. The pump infuses this insulin. Various commercial and academic researchers are conducting research to develop automatically controlled insulin pumps. Still, a reliable fully-closed-loop insulin pump system is not commercially available. One limitation is a closed-loop control system of insulin infusion that can be easily tuned for each individual and adapt to daily variations in the patients characteristics. A control algorithm that provides tight blood glucose control in the presence of large delays associated with insulin absorption, delays between blood and subcutaneous glucose concentration changes, wide inter-subject variability of glucose-insulin dynamics and large intra-subject glycemic disturbances like meal consumption, exercise, or stress is necessary. Most systems under development are based either on proportional-integral-derivative (PID) feedback controllers or model-based predictive control strategies. To date, PID controllers have not yielded successful glucose control strategies for patients under free living conditions. Most model-based predictive control strategies use physiological models representing glucose-insulin dynamics in the body. Their performance is highly dependent on the accuracy of the process model selected to represent the true dynamics of the system. However, most of the physiological glucose-insulin models available are generally representative of an average subject under specific conditions. Nonlinearities and the large number of parameters to be identified make it difficult to tune these models for individual patients.